# Method determine the density of irregular solids as

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Method: Determine the density of irregular solids as follows: 30

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CHAPTER 2. WHAT ARE THE OBJECTS AROUND US MADE OF? - GRADE 10 2.6 1. Measure and record the mass of one of the irregular solids. 2. Tie a piece of thread around the solid. 3. Pour some water into a 100 ml graduated cylinder and record the volume. 4. Gently lower the solid into the water, keeping hold of the thread. Record the combined volume of the solid and the water. 5. Dtermine the volume of the solid by subtracting the combined volume from the original volume of the water only. 6. Repeat these steps for the second object. 7. Complete the table below. Solid Mass (g) Volume (ml) Density (g/ml) Solid 1 Solid 2 Solid 3 2.6 Summary The smallest unit of matter is the atom . Atoms can combine to form molecules . A molecule is a group of two or more atoms that are attracted to each other by chemical bonds. A small molecule consists of a few atoms per molecule. A giant molecule consists of millions of atoms per molecule, for example metals and diamonds. The structure of a molecule can be represented in a number of ways. The chemical formula of a molecule is an abbreviated way of showing a molecule, using the symbols for the elements in the molecule. There are two types of chemical formulae: molecular and empirical formula. The molecular formula of a molecule gives the exact number of atoms of each element that are in the molecule. The empirical formula of a molecule gives the relative number of atoms of each element in the molecule. Molecules can also be represented using diagrams . A ball and stick diagram is a 3-dimensional molecular model that uses ’balls’ to represent atoms and ’sticks’ to represent the bonds between them. A space-filling model is also a 3-dimensional molecular model. The atoms are represented by multi-coloured spheres. In a molecule, atoms are held together by chemical bonds or intramolecular forces . Covalent bonds, ionic bonds and metallic bonds are examples of chemical bonds. A covalent bond exists between non-metal atoms. An ionic bond exists between non- metal and metal atoms, and a metallic bond exists between metal atoms. Intermolecular forces are the bonds that hold molecules together. The kinetic theory of matter attempts to explain the behaviour of matter in different phases. The theory says that all matter is composed of particles which have a certain amount of energy which allows them to move at different speeds depending on the temperature (energy). There are spaces between the particles, and also attractive forces between particles when they come close together. 31
2.6 CHAPTER 2. WHAT ARE THE OBJECTS AROUND US MADE OF? - GRADE 10 Understanding chemical bonds, intermolecular forces and the kinetic theory of matter, can help to explain many of the macroscopic properties of matter.

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